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erofs: dax support for non-tailpacking regular file

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DAX is quite useful for some VM use cases in order to save guest
memory extremely with minimal lightweight EROFS.

In order to prepare for such use cases, add preliminary dax support
for non-tailpacking regular files for now.

Tested with the DRAM-emulated PMEM and the EROFS image generated by
"mkfs.erofs -Enoinline_data enwik9.fsdax.img enwik9"

Link: https://lore.kernel.org/r/20210805003601.183063-3-hsiangkao@linux.alibaba.com
Cc: nvdimm@lists.linux.dev
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
This commit is contained in:
Gao Xiang 2021-08-05 08:36:00 +08:00
parent a08e67a028
commit 06252e9ce0
5 changed files with 107 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/filesystems/erofs.rst
View File

@ -84,6 +84,9 @@ cache_strategy=%s Select a strategy for cached decompression from now on:
It still does in-place I/O decompression
for the rest compressed physical clusters.
========== =============================================
dax={always,never} Use direct access (no page cache). See
Documentation/filesystems/dax.rst.
dax A legacy option which is an alias for ``dax=always``.
=================== =========================================================
On-disk details

42
fs/erofs/data.c
View File

@ -6,7 +6,7 @@
#include "internal.h"
#include <linux/prefetch.h>
#include <linux/iomap.h>
#include <linux/dax.h>
#include <trace/events/erofs.h>
static void erofs_readendio(struct bio *bio)
@ -323,6 +323,7 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
return ret;
iomap->bdev = inode->i_sb->s_bdev;
iomap->dax_dev = EROFS_I_SB(inode)->dax_dev;
iomap->offset = map.m_la;
iomap->length = map.m_llen;
iomap->flags = 0;
@ -382,6 +383,10 @@ static ssize_t erofs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
if (!iov_iter_count(to))
return 0;
#ifdef CONFIG_FS_DAX
if (IS_DAX(iocb->ki_filp->f_mapping->host))
return dax_iomap_rw(iocb, to, &erofs_iomap_ops);
#endif
if (iocb->ki_flags & IOCB_DIRECT) {
int err = erofs_prepare_dio(iocb, to);
@ -402,9 +407,42 @@ const struct address_space_operations erofs_raw_access_aops = {
.direct_IO = noop_direct_IO,
};
#ifdef CONFIG_FS_DAX
static vm_fault_t erofs_dax_huge_fault(struct vm_fault *vmf,
enum page_entry_size pe_size)
{
return dax_iomap_fault(vmf, pe_size, NULL, NULL, &erofs_iomap_ops);
}
static vm_fault_t erofs_dax_fault(struct vm_fault *vmf)
{
return erofs_dax_huge_fault(vmf, PE_SIZE_PTE);
}
static const struct vm_operations_struct erofs_dax_vm_ops = {
.fault = erofs_dax_fault,
.huge_fault = erofs_dax_huge_fault,
};
static int erofs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
if (!IS_DAX(file_inode(file)))
return generic_file_readonly_mmap(file, vma);
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
return -EINVAL;
vma->vm_ops = &erofs_dax_vm_ops;
vma->vm_flags |= VM_HUGEPAGE;
return 0;
}
#else
#define erofs_file_mmap generic_file_readonly_mmap
#endif
const struct file_operations erofs_file_fops = {
.llseek = generic_file_llseek,
.read_iter = erofs_file_read_iter,
.mmap = generic_file_readonly_mmap,
.mmap = erofs_file_mmap,
.splice_read = generic_file_splice_read,
};

4
fs/erofs/inode.c
View File

@ -174,6 +174,10 @@ static struct page *erofs_read_inode(struct inode *inode,
inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec;
inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec;
inode->i_flags &= ~S_DAX;
if (test_opt(&sbi->ctx, DAX_ALWAYS) && S_ISREG(inode->i_mode) &&
vi->datalayout == EROFS_INODE_FLAT_PLAIN)
inode->i_flags |= S_DAX;
if (!nblks)
/* measure inode.i_blocks as generic filesystems */
inode->i_blocks = roundup(inode->i_size, EROFS_BLKSIZ) >> 9;

3
fs/erofs/internal.h
View File

@ -83,6 +83,7 @@ struct erofs_sb_info {
struct erofs_sb_lz4_info lz4;
#endif /* CONFIG_EROFS_FS_ZIP */
struct dax_device *dax_dev;
u32 blocks;
u32 meta_blkaddr;
#ifdef CONFIG_EROFS_FS_XATTR
@ -115,6 +116,8 @@ struct erofs_sb_info {
/* Mount flags set via mount options or defaults */
#define EROFS_MOUNT_XATTR_USER 0x00000010
#define EROFS_MOUNT_POSIX_ACL 0x00000020
#define EROFS_MOUNT_DAX_ALWAYS 0x00000040
#define EROFS_MOUNT_DAX_NEVER 0x00000080
#define clear_opt(ctx, option) ((ctx)->mount_opt &= ~EROFS_MOUNT_##option)
#define set_opt(ctx, option) ((ctx)->mount_opt |= EROFS_MOUNT_##option)

59
fs/erofs/super.c
View File

@ -11,6 +11,7 @@
#include <linux/crc32c.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/dax.h>
#include "xattr.h"
#define CREATE_TRACE_POINTS
@ -355,6 +356,8 @@ enum {
Opt_user_xattr,
Opt_acl,
Opt_cache_strategy,
Opt_dax,
Opt_dax_enum,
Opt_err
};
@ -365,14 +368,47 @@ static const struct constant_table erofs_param_cache_strategy[] = {
{}
};
static const struct constant_table erofs_dax_param_enums[] = {
{"always", EROFS_MOUNT_DAX_ALWAYS},
{"never", EROFS_MOUNT_DAX_NEVER},
{}
};
static const struct fs_parameter_spec erofs_fs_parameters[] = {
fsparam_flag_no("user_xattr", Opt_user_xattr),
fsparam_flag_no("acl", Opt_acl),
fsparam_enum("cache_strategy", Opt_cache_strategy,
erofs_param_cache_strategy),
fsparam_flag("dax", Opt_dax),
fsparam_enum("dax", Opt_dax_enum, erofs_dax_param_enums),
{}
};
static bool erofs_fc_set_dax_mode(struct fs_context *fc, unsigned int mode)
{
#ifdef CONFIG_FS_DAX
struct erofs_fs_context *ctx = fc->fs_private;
switch (mode) {
case EROFS_MOUNT_DAX_ALWAYS:
warnfc(fc, "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
set_opt(ctx, DAX_ALWAYS);
clear_opt(ctx, DAX_NEVER);
return true;
case EROFS_MOUNT_DAX_NEVER:
set_opt(ctx, DAX_NEVER);
clear_opt(ctx, DAX_ALWAYS);
return true;
default:
DBG_BUGON(1);
return false;
}
#else
errorfc(fc, "dax options not supported");
return false;
#endif
}
static int erofs_fc_parse_param(struct fs_context *fc,
struct fs_parameter *param)
{
@ -412,6 +448,14 @@ static int erofs_fc_parse_param(struct fs_context *fc,
errorfc(fc, "compression not supported, cache_strategy ignored");
#endif
break;
case Opt_dax:
if (!erofs_fc_set_dax_mode(fc, EROFS_MOUNT_DAX_ALWAYS))
return -EINVAL;
break;
case Opt_dax_enum:
if (!erofs_fc_set_dax_mode(fc, result.uint_32))
return -EINVAL;
break;
default:
return -ENOPARAM;
}
@ -496,10 +540,16 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
return -ENOMEM;
sb->s_fs_info = sbi;
sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev);
err = erofs_read_superblock(sb);
if (err)
return err;
if (test_opt(ctx, DAX_ALWAYS) &&
!bdev_dax_supported(sb->s_bdev, EROFS_BLKSIZ)) {
errorfc(fc, "DAX unsupported by block device. Turning off DAX.");
clear_opt(ctx, DAX_ALWAYS);
}
sb->s_flags |= SB_RDONLY | SB_NOATIME;
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_time_gran = 1;
@ -609,6 +659,7 @@ static void erofs_kill_sb(struct super_block *sb)
sbi = EROFS_SB(sb);
if (!sbi)
return;
fs_put_dax(sbi->dax_dev);
kfree(sbi);
sb->s_fs_info = NULL;
}
@ -711,8 +762,8 @@ static int erofs_statfs(struct dentry *dentry, struct kstatfs *buf)
static int erofs_show_options(struct seq_file *seq, struct dentry *root)
{
struct erofs_sb_info *sbi __maybe_unused = EROFS_SB(root->d_sb);
struct erofs_fs_context *ctx __maybe_unused = &sbi->ctx;
struct erofs_sb_info *sbi = EROFS_SB(root->d_sb);
struct erofs_fs_context *ctx = &sbi->ctx;
#ifdef CONFIG_EROFS_FS_XATTR
if (test_opt(ctx, XATTR_USER))
@ -734,6 +785,10 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
else if (ctx->cache_strategy == EROFS_ZIP_CACHE_READAROUND)
seq_puts(seq, ",cache_strategy=readaround");
#endif
if (test_opt(ctx, DAX_ALWAYS))
seq_puts(seq, ",dax=always");
if (test_opt(ctx, DAX_NEVER))
seq_puts(seq, ",dax=never");
return 0;
}